semantic-math.github.io

Goals

• provide an AST specification that can describe algebraic, geometric, and other mathetmatical expressions
• provide a set of tools for creating, traversing, transforming, evaluating, solving, and rendering these math ASTs
• encourage interoperability with other tools that adopt the math AST spec

Motivation

There are number of existing JavaScript based tools that parse math expressions using different syntaxes that produce different ASTs which have different capabilities (solving, evaluating, transforming, etc.).

JavaScript over the last few years has seen an explosion of tools for working with its ASTs. One of the things that made the original Parser API AST (and the subsequent competitors) easy to work with is that it's a data-only AST. This means no libraries are necessary to work with it. It also makes it easy to serialize, deserialize, and clone nodes or entire ASTs without any libraries.

My hope is that by providing a spec for an AST with similar properties for math that we might spur a similar explosion in interoperable tools for working with algebraic, geometric, and other mathematical expressions.

The Spec

The math-ast spec is a work in process and needs to be updated to reflect recent changes to the tools. At a very high level it describes Apply nodes which can be used to describe mathematical operations (+, -, ...), functions (sin, log, ...), and relations (=, <, ...) along with a number of atoms such as Numbers, Identifiers. It also aims to describe:

• systems of equations
• sequences and series
• integrals and derivatives
• logic operations
• units of measure
• matrices and vectors
• geometric objects and properties
• sets
• probability
• ...

We're looking to cover elementary math up to under graduate mathematics.

Parts of the spec are influenced by MathML content markup. In particular we borrowed the Apply node and many of the names of functions are the same. The reason why we're not using MathML is that there are:

• it doesn't support things that we'd like support (e.g. units of measure)
• XML is harder to work with than plain old javascript objects
• the way subtraction and negation is handled makes it harder to work with expressions

Tools

math-parser

This provides an example parser that produces an AST conforming to the spec. This is meant as an example parser that people can use in their projects, but if people want to use a different syntax they are encourage to create their own parser that also produces an AST that conforms to the spec.

This project also includes print and toTeX functions which can be used to output an AST to a string that can be reparse to produce the same AST or a TeX string that could be used to render a typeset version of the expression.

It also includes an evaluate function which can be used to evaluate the value of an expression. We plan to pull this out into its own repo and expand its functionality. In particular we'd like evaluate to be able to:

• evaluate an expression with identifiers give a dictionary that supplies the values of those identifiers
• evaluate an expression using different math libraries, currently we use JavaScript's built-in Math library.

math-traverse

It exports traverse and replace functions and is modelled after estraverse.

Being able to traverse and transform an AST key operations when working with ASTs. This library is used in math-parser and math-rules.

math-rules

Writing AST transforms is difficult. The goal of this library is to provide functions for easily describing AST transforms and applying them.

Because we don't want to lock people into the syntax defined by math-parser, the libraries functions take ASTs describing the patterns being matched instead of string. We will be providing factory functions that will take parse and print function and return functions that provide the libraries functionality using the syntax of the given parser.

import {
    defineRuleFactory,
    canApplyRuleFactory,
    applyRuleFactory,
} from 'math-rules'

const defineRule = defineRuleFactory(parse)
const canApplyRule = canApplyRuleFactory(parse)
const applyRule = applyRuleFactory(parse, print)

const rule = defineRule('#a^#p * #^#q', '#a^(#p + #q)')
const output = applyRule('x^2 * x^5')
console.log(output)  // x^(2 + 5)

Note: the factory functions still need to be writen.

It currently exposes defineRule, applyRule, canApply rule functions which can be used with ASTs directly.

import {definRule, canApplyRule, applyRule} from 'math-rules'
import {parse, print} from 'math-parser'  // could be another math-ast compatible parser

const rule = defineRule(parse('#a^#p * #^#q', '#a^(#p + #q)'))
if (canApplyRule(rule, parse('x^2 * x^5'))) {
    const output = applyRule(rule, parse('x^2 * x^5'))
    console.log(print(output))
}

math-nodes

This library doesn't do much yet, but the plan is to house a set of common functions for building nodes and performing various checks on nodes. Although, both of these can be handled manually it's these helper functions will make it easier.

A number of these functions are defined in math-parser and math-rules so we just need to extract them into a new library.

Future Work

Much of the work currently being done is to help mathsteps migrate from mathjs to math-parser and math-rules. The hope is that this work will be useful for other projects and developers as well.

Mathsteps Milestones

We'd also like to have tools that:

• update the spec to match what math-parser is currently producing
• validate math ASTs to check that they conform to the spec
• typeset and render math ASTs